Backing for artificial teeth



Jan. 28, 1936. H, FREEDMAN ZMZQJEI BACKING FOR ARTIFICIAL TEETH Filed Jan. 29, 1934 ATTORN 6 Patented Jan. 28, 1936 UNITED STATES PATENT OFFICE BACKING FOR ARTIFICIAL TEETH Hyman Freedman, Brooklyn, N. Y. Application January 29, 1934, Serial No. 708,715

1 Claim.

This invention relates to improvements in dental bridge-work and has particular reference to a novel construction of backing for an artificial tooth or facing.

In bridge-work construction it has been well known to mount a tooth upon a backing and to provide for the replacement of the tooth when the latter becomes broken or damaged. One type of such'construction which is quite generally employed involves the formation, in the rear surface of the facing or tooth, of a vertical groove of substantially keyhole shape which extends from a point near the cutting edge or incisal tip of the tooth to the other end thereof which fits against the gum, The associated backing is made in the form of a fiat plate having a centrally and vertically disposed post of the same configuration throughout its length as the groove in said'facing and of substantially the same cross-sectional dimensions as said groove so as to fit snugly therein when assembling the parts. Due to this snug fit the assembly operation, which is performed by initially inserting one end of the post into the open or gum end of the groove and then moving one of the parts longitudinally with respect to the other until the same are in proper relative positions, must necessarily be accomplished with the outer surface of the fiat backing plate and the inner surface of the tooth in precise parallel relation since the snug fit of the post in the groove precludes any possibility of one of the elements assuming an angle relative to the other. Such a construction has been productive of some satisfactory results among which may be mentioned the prevention of lateral displacement of the tooth with respect to its backing and the vertical 'adjustability of said tooth. This latter feature is particularly desirable in properly positioning the tooth on the backing and in connection with the replacement of a broken or damaged tooth. Quite often it is found that an exact reproduction of a defective tooth is unavailable and, as a consequence, a replacement of more or less slightly different form has to be used. This necessitates a vertical adjustment of the tooth on the backing so as to precisely fit the gum and properly locate the biting edge of the tooth. Such operation may be readily accomplished with the post and groove construction referred to. However, such a construction does not provide a sufficiently adequate protection for the tooth, particularly with reference to the incisal or cutting edge thereof where the greater portion of the strain or force of chewing is applied.

It has been heretofore suggested to provide a protective flange or ledge on the backing which engages and covers the incisal tip of the tooth but, in such devices as are at present known, a special facing has to be employed and the desirable features of the above referred to construction, such as the vertical adjustability, are not obtainable. The provision of such a protective ledge, in the case of the latter mentioned construction which involves the fiat backing plate, is not feasible since the ledge would interfere with the placing of the backing and tooth in exact parallel relation during the assembly operation. Notwithstanding this drawback, protection of the incisal tip in such construction has been attempted by forming a feather edge on the end of the fiat backing plate contiguous to said tip after the parts have been assembled. Such attempts have proven unsatisfactory because they are ineffectual in properly protecting the tip and once the tooth breaks it is necessary to cut off the feather edge on the backing in order to remove the tooth and apply a replacement in the manner previously mentioned, that is, with the backing plate and tooth in precise parallel relation. This severing of said feather edge must inevitably shorten the backing plate and thereby render it less efiicient each time a new tooth is mounted thereon.

The present invention contemplates the provision of a backing in which is embodied all the advantages of the post and groove construction discussed above, and wherein the backing may be provided with a permanent protective ledge for the incisal tip of the tooth. Such advantages are obtainable, in the present backing, by the simple but effective and novel expedient of providing a post for the backing which will permit of the with respect to the facing or tooth as the parts are being assembled so that during the relative movements of said parts to their ultimate positions the free edge of the protective ledge will be enabled to pass along the rear surface of the tooth until it has cleared the incisal tip thereof, whereupon a lateral movement of one of the parts relative to the other may be effected. to bring the opposed surfaces into parallel relation with the protective ledge covering said incisal tip.

The inventive idea involved is capable of receiving a variety of mechanical expressions one of which, for purposes of illustration, is shown in the accompanying drawing, wherein:

Figure l is a perspective view of a tooth and latter assuming an angular position its backing constructed in accordance with the invention. 7

Figure 2 is a rear elevation of the tooth and.

' its backing.

Figure 3 is a vertical longitudinal section, the dotted lines indicating the relative position of V the elements during the assembly thereof.

Figure 4 is a perspective view of the backing of the present invention.

Figure 5 is a'transverse section on the line 5-5 ofFigure 3, and, p V Figure 6 is afragmentary transverse section on the line 66 of Figure 3.

Referring more particularly to the accompanying drawing, the numeral 1 designates an artificial tooth of porcelain or like material usually employed in bridge-work construction and'hav-' ing the inclined surface 8 adapted to be fitted against the gum, and the incisal tip or cutting edge 9. In the rear surface of the tooth 'Ithe same is provided with a centrally and vertically disposed groove I6 one end of which opens upon the surface 8 while the other end terminates short of the incisal tip 9. Throughout the greater portion of the length of the groove ID the: same is of substantially key-hole shape in cross-section, as best shown in Figures 5 and 6, there being a portion II of the groove adjacent the tip 9 which is merely circular in formation to provide an abutment I2 which aids in preventing lateral displacement of the tooth relative to its backing I3 when the parts are assembled in the manner to appear in the course of the description.

The backing I3 is made of any desirable ma' terial usually employed in the art and is shaped to conform generally to the contour of the tooth which is adapted to be mounted thereon. The

present backing is substantially fiat and is provided at one end with a laterally projecting ledge or flange I4 which. is adapted to engage and cover the incisal tip 9, when the parts are assembled, to provide protection therefor against the stress and strain incident to chewing. Extending from the other end of the backing plate and toward the ledge I4 is the centrally and vertically disposed post generally indicated by the numeral I 5 which is adapted to be disposed within the groove It to interlock the tooth and backing and prevent any relative'lateral displacement ofthe parts. As distinguished from the post of the known backing previously referred to, the post I5 only has a portion'thereof adjacent the gum end ,of the backing shaped to conform to the contour of thegroove I I]. In other words, said end is provided throughout a portion of its length with a reduced shank I6 and a rounded or bulbous portion IT. From the inner end of this latter portion the post is reduced so that the remaining part I8 of the length thereof is "of the same width or thickness as the shank I6 at the inner end of said portion I8, said end is reduced as indicatedat I9 to provide an extension 20-spaced from the backing plate and adapted to extend more or lessv into the portion or recess II of the groove II] when the parts are in the position shown in Figure 3, thus placing the extension, 20 behind the abutment I2 so that the extension will contact therewith and limit any possible lateral displacement. In this connection, itis to benoted that in Figure 3 of the drawing considerable space issh'own between the extension 20 and the abutment I2. This is due to the greatly exaggerated size of the figure, 7

but as a matter of fact, in actual's'ize theparts 3 structure provides for disposing the elements at an angle to eachother as indicated by the dotted lines (Figure 3), in order that the ledge I4 may clear the rear or inner face of the tooth during the relative longitudinal movement necessary to bring the parts to their final positions. This relative angular position is made possible by the 7 novel formation of the post I5, the reduced portion s of which, together with the extension 20, is inserted into the open end of the groove Ill after theinner opposed. surfaces of the tooth and backing, and the groove and post of the respective elements, have been coated with a thin film 22. of

cement or other binder in a plastic state. 7 Inasmuch as said portion I8 is no wider than the restricted portion of said groove, the backing will be permitted to assume an angular position'rela- .tive to the tooth at least sufiicient to allow the 'free edge of the ledge I4 to clear the adjacent surfaces of the tooth and move along the same until the said dotted line position of Figure 3 is reached. Then a slight lateralor pivotal move- 'ment ofthe parts will bring said opposed surfaces into parallel and substantiallyabuttingrelation with the ledge I4 engaging the incisal tip 9. The

post I5 will then assume the full line position of Figure 3 with the portion I1 thereof centered in the rounded portion of the groove I0 so as to prevent any undue lateral displacement of the parts at the adjacent end of the tooth in the same manner that such displacement is avoided by the extension 20 which rests behind the abutment I2.

The cement is then permitted to hardenwith the result that the elements are assembled into practically a unitary structure.

Should a replacement of the tooth be necessary,

the foregoing assembly operation may be reversed, after softening the cement, to remove the damaged tooth. 'The new facing is then applied to the backing and if this replacement should be longer, for instance, than the original tooth it may be adjusted upwardly or downwardly'as the case may be, until the ledge I4 is in engagement .with the tip 9. In the event that the portion II of the groove II] should not be deep enough to accommodate the extension 20 and thus prevent the proper positioning of the ledge l4, a sufficient portion of the free end of said extension may be severed to allow the ledge to assume its proper positioning; and should the gum end 8 of the tooth project too far and thus prevent proper fitting to the gum, said end may be ground down to the correct size. Thus, by reason of the longitudinal adjustability of the tooth or the backing, the latter affords the possibility of utilizing teeth of slightly different dimensions and at the same 'time provides a permanent protective ledge for the incisal tip of any tooth capable of application thereto.

What is claimed is: r r

In a dental bridgework, an artificial tooth pro vided in its rear surface with a groove extending from the inner end of the tooth to a point short of the incisal tip thereof and having cross-sectional areas of different widths, and a backing having a ledge engageable with the incisal tip of said tooth and provided with a post insertable into said groove, said post having one portion conforming to the contour of the difierent cross-sectional areas of said groove and another portion conforming only to the smaller cross-sectional area of the groove, both of said portions being of 10 smaller dimensions than the corresponding areas of said groove so as to provide a space between the walls of the latter and said post, whereby the inner adjacent faces of the tooth and backing may assume a relative angular position until said post is entirely inserted int-o said groove, said tooth and backing thereafter having relative lateral movement to abut said faces and thereby engage said ledge with said incisal tip, and the total length of said post being less than that of said groove.

HYMAN FREEDMAN. 

